An air bag, which restrains an occupant by its expansion into a vehicle compartment when an automobile is impacted, is sometimes housed in a retainer in a state of being wrapped in a packing cloth in order to stabilize its folded state. For example, Patent Document 1 discloses an air bag device in which a folded air bag is wrapped in the packing cloth, and upon collision of a vehicle, the air bag is expanded by gas generated from an inflator, to break the packing cloth as well as to cleave the lid, and is then expanded into the vehicle compartment. The packing cloth is formed with an opening portion for checking a folded state of the air bag. Further, the lid is adapted to be cleaved at a central tear line thereof, to be both-opened.